The initial values for the differential and difference equations are taken to be zero for a TransferFunctionModel. For the state-space models, they are taken to be the state operating values of sys unless specified.

OutputResponse[{sys,{x10,x20,…,xn0}},…] can be used to specify the initial state for a state-space model sys.

For descriptor state-space systems, the initial states need to be consistent.

For delay state-space systems, the initial states include history and can be given as for t≤0.»